The present invention relates to bore sight collimators that are used to align a sight with the bore of a gun.
At present an optical boresighter uses an optical collimating system consisting of a lens that is optically aligned with a reticule marked on a glass plate, positioned at the focal plane of the lens. The lens and the reticule plate are mounted at either end of a housing.
The alignment of the collimator housing to the bore of the gun is achieved by use of a close fitting pin inserted into the end of the barrel, to which the collimator housing is clamped. Alternatively a magnetic strip is built into to the collimator housing, such that the collimator can be attached to the end of a gun barrel magnetically. The end of the barrel is by necessity, square with the bore, and this gives the necessary alignment.
In both these systems the optical element of the collimator is relatively large, it is similar to, or larger in size, to the objective lens of a riflescope. When the collimator is viewed with a riflescope, only the collimator reticule and the riflescope cross wires can be seen.
A large aperture of the optical element requires the optical path length to be long and consequently the collimator housing is large.
To prevent internal fogging, the void between the lens and the reticule plate is usually filled with dry Nitrogen gas, and the housing is usually of metal construction to contain the gas, which results in a relatively heavy unit.